The present invention relates to a variable displacement swash plate compressor.
Japanese Laid-Out Patent Publication Nos. 5-172052 and 52-131204 describe conventional variable displacement swash plate compressors (hereafter simply referred to as the compressors). The compressors each have a housing including a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores. A rotatable drive shaft is supported in the housing. A swash plate that is rotatable together with the drive shaft is arranged in the swash plate chamber. A link mechanism is located between the drive shaft and the swash plate to allow the inclination angle of the swash plate to change. The inclination angle refers to an angle relative to a direction orthogonal to the rotation axis of the drive shaft. Each cylinder bore accommodates a piston. The piston reciprocates in the cylinder bore and defines a compression chamber in the cylinder bore. A conversion mechanism coverts rotation of the swash plate to reciprocation of the piston in each cylinder bore. The stroke when the piston reciprocates is in accordance with the inclination angle of the swash plate. The inclination angle of the swash plate is changed by an actuator, which is controlled by a control mechanism.
The compressor described in Japanese Laid-Out Patent Publication No. 5-172052 includes a pressure regulation chamber in a rear housing member, which is an element of the housing, and a control pressure chamber in a cylinder block, which is also an element of the housing. The control pressure chamber is in communication with the pressure regulation chamber. The actuator is located in the control pressure chamber. The actuator is not rotated integrally with the drive shaft. More specifically, the actuator includes a non-rotation movable body that covers the rear end of the drive shaft. The non-rotation movable body includes an inner wall surface that supports the rear end of the drive shaft so that the rear end is rotatable. The non-rotation movable body is movable along the rotation axis of the drive shaft. Although the non-rotation movable body moves in the control pressure chamber along the rotation axis of the drive shaft, the non-rotation movable body is not allowed to rotate about the rotation axis of the drive shaft. A spring that urges the non-rotation movable body toward the front is arranged in the control pressure chamber. The actuator includes a movable body, which is coupled to the swash plate and movable along the rotation axis of the drive shaft. A thrust bearing is arranged between the non-rotation movable body and the movable body. A pressure control valve, which changes the pressure of the control pressure chamber, is arranged between the pressure regulation chamber and the discharge chamber. A change in the pressure of the control pressure chamber moves the non-rotation movable body and the movable body in the axial direction of the drive shaft.
A link mechanism includes a movable body and a lug arm, which is fixed to the drive shaft. The rear end of the lug arm includes an elongated hole, which extends in a direction orthogonal to the rotation axis of the drive shaft and in a direction extending from the radially outer side toward the rotation axis of the drive shaft. The front of the swash plate is supported by a pin inserted to the elongated hole so that the swash plate is pivotal about a first pivot axis. The front end of the movable body includes an elongated hole, which extends in a direction orthogonal to the rotation axis of the drive shaft and in a direction extending from the radially outer side toward the rotation axis. The rear end of the swash plate is supported by a pin inserted to the elongated hole so that the swash plate is pivotal about a second pivot axis, which is parallel to the first pivot axis.
In this compressor, the pressure control valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the front. Thus, the inclination angle of the swash plate increases, the piston stroke is lengthened, and the compression displacement is increased for each rotation of the drive shaft. When the pressure control valve closes to disconnect the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the rear. Thus, the inclination angle of the swash plate decreases, the piston stroke is shortened, and the compressor displacement is decreased for each rotation of the drive shaft.
In the compressor of Japanese Laid-Open Patent Publication No. 52-131204, the actuator is rotatable integrally with the drive shaft in the swash plate chamber. More specifically, the actuator includes a partitioning body fixed to the drive shaft. The partitioning body accommodates a movable body, which is movable relative to the partitioning body along the rotation axis. A control pressure chamber is defined between the partitioning body and the movable body to move the movable body with the pressure of the control pressure chamber. A communication passage, which is in communication with the control pressure chamber, extends through the drive shaft. A pressure control valve is arranged between the communication passage and the discharge chamber. The pressure control valve is configured to change the pressure of the control pressure chamber and move the movable body relative to the partitioning body along the rotation axis. The movable body includes a rear end that is in contact with a hinge ball. The hinge ball pivotally couples the swash plate to the drive shaft. A spring, which urges the hinge ball in the direction that increases the inclination angle of the swash plate, is arranged at the rear end of the hinge ball.
A link mechanism includes the hinge ball and a link, which is located between the partitioning body and the swash plate. A pin, which extends in a direction orthogonal to the rotation axis, is inserted to the front end of the link. A pin, which also extends in a direction orthogonal to the rotation axis, is inserted to the rear end of the link. The swash plate is pivotally supported by the link and the two pins.
In this compressor, a pressure regulation valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the movable body toward the rear. Thus, the inclination angle of the swash plate decreases and shortens the stroke of the pistons. This decreases the compressor displacement for each rotation of the drive shaft. When the pressure regulation valve closes and disconnects the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as the swash plate chamber. This moves the movable body toward the front. Thus, the inclination angle of the swash plate increases and lengthens the stroke of the pistons. This increases the compressor displacement for each rotation of the drive shaft.
In the compressor of Japanese Laid-Open Patent Publication No. 5-172052, the non-rotation movable body of the actuator moves in the axial direction at the rear end of the drive shaft. This increases the overall axial length.
In this compressor, when rotation is produced at the inner circumferential surface of the non-rotation movable body, axial movement is produced at the inner circumferential surface and the outer circumferential surface of the compressor. This may result in insufficient lubrication around the non-rotation movable body and adversely affect the movement characteristics of the actuator. In such a case, it may become difficult to change the inclination angle of the swash plate adequately, and the compressor displacement may not be controlled in the preferred manner by lengthening and shortening the piston stroke. Further, in this compressor, wear or the like is apt to occur around the actuator. This may adversely affect the durability of the compressor.
In the compressor of Japanese Laid-Open Patent Publication No. 52-131204, the actuator is located closer to the rotation axis than the link of the link mechanism. Thus, the control pressure chamber of the actuator is small in the radial direction, and it is difficult to urge the swash plate with the movable body. Further, in this compressor, due to the link mechanism, it is difficult to supply the actuator with lubrication oil. This may result in insufficient lubrication of the actuator and adversely affect the movement characteristics of the actuator. Accordingly, it may become difficult to change the inclination angle of the swash plate, and the compressor displacement may not be controlled in the preferred manner.